Improvement in grinding and polishing wheels



M; Zr r Z M Z M G. HART. Grindingand Polishing'wheel.

first put into the mold.

UNITED STATES PATENT OFFICE.

GILBERT HART, OF DETROIT, MICHIGAN.

IMPROVEMENT IN GRINDING AND POLISHING WHEELS.

Specification forming part of Letters Patent No. 215,351, dated May 13,1879; application filed October 31, 1878.

To all whom it may concern:

Be it known that I,GILBERT HART, of Detroit, in the county of Wayne andState of Michigan, have invented certain new and useful Improvements inGrinding and Polishing Wheels, of which the following is aspecification.

The object of this invention is to strengthen emery, corundum, or othercomposition grinding and polishing wheels against centrifugal strainduring high speed of rotation.

It' is known to persons who use grinding and polishing wheels that inorder to obtain the best effect therefrom they should be run at a highrate of speed; and it is also known that when thus used these wheels, asheretofore made, even when used with great care and skill, are liable-tobreak and fly off with great violence in fragments from their axlesunless the wheels are braced in some manner against the greatcentrifugal strain to which they are subjected. This bracing hasheretofore been done by embedding in the wheel metallic bars, plates, ora wire web, and this manner of bracing has proven very satisfactory, asthe bars, plates, or wires are only required to have small transversedimensions, and may always extend from center to periphery of thewheels, wearing away evenly with said periphery, and not interferingwith the efficiency of its working-surface. It, however, necessitatesconsiderable care in the manufacture of wheels, as in the molding aportion of the composition of which a wheel is to be formed must befirst placed in the mold, the bars, plates, or wire web cut to theproper size and partially embedded therein, properly arranged, and thenthe other portion of the composition is placed or poured upon the bars,plates, or wires,. sinking between them and becoming incorporated withthe composition These metallic braces are also good conductors of heat,and are liable to conduct the heat occasioned by friction to the'centerand intermediate portions of the wheel, causing an expansion, which hasa tendency to split the wheel. The contraction of such braces after theexpansion occasioned by the heat from use also occasions a temporaryunevenness of the working-surface of the wheel The fibers of asbestusserve admirably as a 7 binding medium for the composition of which thewheel may be formed, so as to brace it against centrifugal strain whenin use. It is a very poor conductor of heat, and therefore communicatesnone of the heat resulting from the friction of use toward the center ofthe wheel. Its expansion and contraction under variations of temperatureare practically inappreciable, so that the evenness of the grinding orpolishing surface of the wheel is not affected thereby, and it wearsaway evenly with the composition of which the mainpart of the wheel isformed.

My improved wheel is molded in the same manner as the ordinary emery orcorundum wheel, the composition being prepared in the ordinary way, andthe asbestus is then mixed thoroughly therewith, in the proportion ofabout one part in bulk of asbestus to four parts of the composition withwhich it is mixed. The wheels thus made may be used as are ordinarygrinding and polishing wheels.

In Figure lof the accompanying drawings is shown a grinding andpolishing wheel constructed according to my invention, the letter Aindicating the wheel, formed of a composition of emery or corundum, orother suitable material or materials having mixed therewith fibrousasbestus, which is designated by fragmentary lines. Fig. 2 represents anedge view of the wheel.

I am aware that asbestus has been used as a binding element infire-proof coatings and artificial stone, as shown in the patents toAntonio Pelletier, granted February 18, 1868, and numbered 74,587, andMay 5,1868, and numbered 7 7,705; but it is obvious that such artificialstones are not adapted for usein grind ing and polishing wheels, as theyare themselvessusceptible of receiving a high polish.

My invention consists not in the simple use of asbestus as a bindingelement of artificial stone, but in the application of the discoverythat this substance will act as a binding ingredient for a compositionin which emery or corunclum is the preponderating element, and which isadapted for use in grinding and polishing wheels, and that the abradingqualities of the composition are not injuriously affected by theaddition of such binding ingredient.

What I claim is A grinding or polishing Wheel containing an In testimonythat I claim the foregoing I have hereunto set my hand in the presenceof the subscribing witnesses.

GILBERT HART.

Witnesses J AS. A. J ONES, PHI. Roo s.

